One more note, the Jump Break feature does not change how your post appears in your feed. You can configure post feed options by going to
Settings | Basic | Site Feed, and editing
Allow Blog Feeds.
Update: Users that have customized their
Blog Posts widget or otherwise have highly customized templates: You may need to edit your HTML to enable Jump Breaks. First,
back up your template, then follow the instructions at the bottom of this
help article.
This is one of many features announced as part of Blogger's 10th birthday. Happy Birthday!